Backfire from carbs, poor performance

[flyfish]

Whoa Nelly.

 

Your TDC mark on the crank pulley is the SECOND notch (slightly larger), NOT the first on as you photographed...

[datzenmike]

Well at 5 degrees per notch you are still only a few degrees above the 12. I'm not familiar with the L 16 pulley notches. Set 12 @ TDC.

 

Vacuum is excellent. This will leave a lean carb. Pull plugs. The white ones are the carb with the problem.

[Thepspack]

Crap!  I reset the distributor and cam off the first mark.  So I've got everything retarded…

[banzai510(hainz)]

 I reset the distributor and cam off the first mark.

 

 

I would have ran the car first with the stock set up just to make sure you got the mechainical and electrical correct..Maybe SUs are just junk what you have????????

also adding a different or the wrong coil with do the same on a point ignition  system causes the points to arch out. anthing else was change we need to know.

 

 

Big mark on L16 crank is the Zero mark

 

also setting sprocket to #2 is nothing wrong wesp with a aftermarket cam. shouls till work fine

If you have a Jap chain its marked with the brite links to put on the dimples on sprockets

 

http://vimeo.com/19077890

[Thepspack]

I went back through and checked everything thing out with the engine at TDC on the second bigger mark.  The cam lines up perfectly now, the distributor drive was a tooth out as well, so I fixed that.  Started it back up and reset the timing at 12 degrees.  Runs noticeably better now, vacuum at 20pds steady, feels a little cooler too.  Took it on a test drive, more power off idle.  Still a little stumbling as it approaches 3k, but almost no backfiring out of the carbs.  I'm thinking thats the needles still.  

 

As for the parts on the engine:

A87 peanut, ported to 1.5"

SSS intake

ZT Su's w/ M143 needles

Stock L16 cam

L16 stock pistons

All bottom end stock L16

Points distributor w/ Pertronics, Accel coil 

 

I took a little video so you guys can listen, hopefully you guys can here it.  There was one backfire in there just after I took off other that that it did pretty good.  

 

 

 

[flatcat19]

Sounds like you're on your way! 

[ggzilla]

Congratulations

[datzenmike]

ZT Su's w/ M143 needles

ZT SUs??? Do you mean 46mm Z car SUs??? These are a bit large even for an L20B.

[wayno]

ZT is Ztherapy  

 

ZT SUs??? Do you mean 46mm Z car SUs??? These are a bit large even for an L20B.

[Thepspack]

38mm SU's rebuilt by Z Therapy.

[datzenmike]

Perfect.

[Thepspack]

Thanks for the help everyone, once I start modifying needles that should take care of the stumbling.

[banzai510(hainz)]

just to let you know if you run a pertronix you should still run the ballast resisitor like the stock set up.

accell coil there is the "super stock" which is just a stock equiv and should run the stock ballast.
If you run the SUPERCOIL. then you add the ballast that comes with the SUPERCOIL with the stock ballast

 

running no ballast on a point coil with heat the coil up and maybe fail. and or burn the Pertronix out.   Same with the Mallory unilites

[datzenmike]

 

Vacuum is excellent. This will leave a lean carb. Pull plugs. The white ones are the carb with the problem.

 

 

[Thepspack]

I figured the Accel coil did not need the ballast resistor.  After reading this I went out and felt the coil after driving the truck a few miles home from work.  Holy shit it was hot, too hot to touch.  Unfortunately the PO pulled all the wires going to the resistor and I have no clue what go's where.  There are a bunch of wires coming out of the harness there.  

 

 

Well at 5 degrees per notch you are still only a few degrees above the 12. I'm not familiar with the L 16 pulley notches. Set 12 @ TDC.

Vacuum is excellent. This will leave a lean carb. Pull plugs. The white ones are the carb with the problem.

 

Tried doing a plug chop, They all look the same, kind of grayish,  I'm assuming the idle is slightly rich,  then when I hold the truck around 3k, it go's lean and whitens them up.

 

 

[banzai510(hainz)]

Daniel or datzenmike has the dwawing for this but what I remember on 521s youll run the blk white wire to the ballast. then theres a blk red that come out of the ballast ( 2 wires on it.. and the other end goes to the + side coil.

 

that blk red will have 12volt with key on start(remove the starter wire and try it out.

blk white will be key ON

[wayno]

Daniel or datzenmike has the dwawing for this but what I remember on 521s youll run the blk white wire to the ballast. then theres a blk red that come out of the ballast ( 2 wires on it.. and the other end goes to the + side coil.

 

that blk red will have 12volt with key on start(remove the starter wire and try it out.

blk white will be key ON

This above is correct, black/white line wire goes to the ballast(comes from the fuse block), the black/red line wire goes directly to the positive side of the coil(comes from the ign. switch).

You can always tell when the black/red line wire is not connected, it doesn't hit at all when turning over, but the moment you let off when the engine is warm it starts, but when it is cold(the engine), it's a bitch to get started, I finally figured out if I used a jumper wire in the morning(batt. to positive side of coil), my day started out with a more positive attitude.

 

 

I finally figured out the issue, and re-connected the black/red line wire that had been removed for some reason.

[Thepspack]

Thanks, I'll check it out when I get back from duty.

[Thepspack]

I finally returned from playing army and installed my O2 sensor.  At idle it's between 11-12, thats about right.  Once I begin to accelerate it begins to lean out, at 2500 RPM the gauge hits 17, then go's off the charts lean as It nears 3000 RPM.  Time to start modding needles.  :D

[Sealik]

11-12 is a little rich for idle...... 14s are better.

Since you can't add material to the needle...you might be able cheat a bit and raise the jets which will lean it out, then profile the needles

[Thepspack]

So I spent a few hours measuring and sanding needles with great success.  At Idle the gauge sits between 13-14, under acceleration it's around 12, cruising on the freeway it's at 14.  Runs bitchen, couldn't be happier, never thought a few thousandths would make such a big difference.  Thanks everyone for the help.